Section 4 (5-4) Rocks From Reefs

Vocabulary

coral reef- a structure formed from a lot of coral animals
atoll- an island that is donut-shaped island far from shore

Coral animals are relatives of jellyfish and their size is about the size of the fingernail or smaller.
Each one looks like an small sack with a mouth which is surrounded by tentacles.
They eat microscopic creatures which is caught by the tentacles.
The corals form a skeleton that grows together and that makes the structure called coral reef.
- They only form in warm, and shallow tropical oceans.
- They can't grow in cold or low-in-salt oceans.
In U.S., they only grow on coasts of southern Florida and Hawaii.
There is an tiny algae growing in each coral animal and it provides the substance which coral animals need to live.
- Algae need sunlight, so most coral reefs occur within 40 meters from surface.
  - There are not enough sunlight below 40 meters from surface.